Amperometric biosensor with enzyme amplification fabricated using self-assembled monolayers of alkanethiols: the influence of the spatial distribution of the enzymes

The influence of the spatial distribution of the two enzymes in an amplifie d enzyme electrode is investigated by the step-wise fabrication of the enzy me interface. The two enzymes, glucose oxidase (GOD) and glucose dehydrogen ase (GDH), are co-immobilised onto the surface of a gold electrode modified with the alkanethiol, 3-mercaptopropionic acid. Three geometries were fabr icated: (1) a monolayer enzyme electrode where both enzymes were covalently attached to the alkanethiol layer, (2) a bilayer electrode when the inner layer was GOD and the outer layer was GDH, and (3) a bilayer sensor where t he inner layer was GDH and the outer layer was GOD. The response of the thr ee geometries was shown to vary with regard to linear range, sensitivity an d hence gain. We believe this is the first demonstration of the spatial rel ationship between enzymes in a multi-enzyme system influencing the response of the resultant enzyme electrode. (C) 2000 Elsevier Science S.A. All righ ts reserved.